From 5b4c559d4dcdc42bf2acef179d3e83590a6c79b6 Mon Sep 17 00:00:00 2001
From: Aithal <aithal@amazon.com>
Date: Mon, 22 May 2017 13:09:19 -0700
Subject: [PATCH] pkg/types: safer typecasting for TextUnmarshaler when loading
 args

types.LoadArgs does an unsafe typecast for env args key value pairs.
This can cause a panic if the config type fields do not implement
the encoding.TextUnmarshaler interface. This commit modifies it to
do a safe type cast and return an error in such scenarios.
---
 pkg/types/args.go      |  7 +++++--
 pkg/types/args_test.go | 11 +++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/pkg/types/args.go b/pkg/types/args.go
index 66dcf9e..e87c6b6 100644
--- a/pkg/types/args.go
+++ b/pkg/types/args.go
@@ -85,8 +85,11 @@ func LoadArgs(args string, container interface{}) error {
 			unknownArgs = append(unknownArgs, pair)
 			continue
 		}
-
-		u := keyField.Addr().Interface().(encoding.TextUnmarshaler)
+		keyFieldIface := keyField.Addr().Interface()
+		u, ok := keyFieldIface.(encoding.TextUnmarshaler)
+		if !ok {
+			return fmt.Errorf("ARGS: '%s' cannot be unmarshalled from textual form for pair %q", keyField, pair)
+		}
 		err := u.UnmarshalText([]byte(valueString))
 		if err != nil {
 			return fmt.Errorf("ARGS: error parsing value of pair %q: %v)", pair, err)
diff --git a/pkg/types/args_test.go b/pkg/types/args_test.go
index 3a53d9a..23772ca 100644
--- a/pkg/types/args_test.go
+++ b/pkg/types/args_test.go
@@ -118,4 +118,15 @@ var _ = Describe("LoadArgs", func() {
 			Expect(err).NotTo(HaveOccurred())
 		})
 	})
+
+	Context("When known arguments are passed and cannot be unmarshalled", func() {
+		It("LoadArgs should fail", func() {
+			conf := struct {
+				IP IPNet
+			}{}
+			err := LoadArgs("IP=10.0.0.0/24", &conf)
+			Expect(err).To(HaveOccurred())
+
+		})
+	})
 })
-- 
2.44.0